Preparation method of novel polyacrylic acid water treatment agent

Abstract

The invention aims to prepare a polyacrylic acid water treatment agent with scale inhibition performance and a branched structure, and the method comprises the following steps: synthesizing polyacrylic acid from acrylic acid under the action of an initiator by adopting an aqueous solution polymerization method, grafting the polyacrylic acid to a polyacrylic acid chain in a ring opening manner by utilizing a monomer glycidyl methacrylate, and branching the structure of the polyacrylic acid water treatment agent to obtain the scale inhibitor. The scale inhibition performance of the polyacrylic acid is slightly higher than that of industrial standard polyacrylic acid.

Description

Technical Field

[0001] The present invention belongs to the field of polymer technology, and particularly relates to the synthesis of polyacrylic acid water treatment agent and a series of characterizations thereof. Background Art

[0002] Industrial circulating cooling water will scale to varying degrees with carbonates, etc., resulting in blockage and leakage of heat exchangers and pipelines, seriously affecting the cooling effect, reducing production efficiency and production capacity, and bringing great hidden dangers to industrial production. With the development of the economy and the progress of technology, water treatment technology and environmental protection issues have received increasing attention. According to the characteristics of the circulating cooling water system and the nature of the water quality, the reasonable use of scale inhibitors can reduce the scale in the system, extend the service life, and achieve the purpose of water conservation and energy saving. So far, polyacrylic acid (PAA) is the most common water treatment agent. Because it contains abundant carboxyl groups (-COOH), it can complex with a variety of metal ions to remove metal ions in water and achieve the purpose of scale inhibition. Acrylic acid (AA) is polymerized into PAA under the action of initiator ammonium persulfate.

[0003] Chain initiation:

[0004]

[0005] Chain growth:

[0006]

[0007] Glycidyl methacrylate (GMA) can be grafted onto the polymer due to the presence of highly active acrylate double bonds, and the epoxy groups contained can react with a variety of functional groups to form functionalized polymers. To improve the scale inhibition performance of PAA, the polymer structure is regulated, and AA reacts with GMA to synthesize a polymer with a branched structure.

[0008] Branching process:

[0009]

[0010] Technical solutions of the prior art

[0011] There are many synthesis methods for low molecular weight PAA, mainly including aqueous solution polymerization method, inverse suspension polymerization method, inverse emulsion polymerization method, etc. The aqueous solution polymerization method is to dissolve the monomer, initiator and chain transfer agent in water for reaction. The inverse suspension polymerization method uses the monomer as the water phase (the initiator and chain transfer agent are dissolved in the water phase), and a low-boiling organic solvent as the oil phase (suspending agent) for polymerization reaction. The inverse emulsion polymerization method is to add an emulsifier in the dispersion medium (oil phase) to reach the critical micelle concentration, stir to make the emulsifier disperse evenly, heat to the reaction temperature after introducing nitrogen, and then dropwise add a solution containing monomer, initiator, chain transfer agent and water.

[0012] Disadvantages of the prior art

[0013] The product synthesized by the inverse suspension polymerization method has a high molecular weight, a relatively wide molecular weight distribution, complex subsequent processing, and is not suitable for preparing polyacrylic acid with scale inhibition performance; the preparation process and subsequent processing of the inverse emulsion polymerization method are relatively complicated, and it is also not suitable for preparing polyacrylic acid with scale inhibition performance. Summary of the invention

[0014] 1. Technical problems to be solved by the present invention

[0015] The purpose of the present invention is to prepare a polyacrylic acid water treatment agent with scale inhibition performance, so that it can basically achieve the scale inhibition performance of industrial standard polyacrylic acid, and branch its structure to functionalize it.

[0016] 2. Technical solution

[0017] (1) Add 5 mL of ultrapure water to a distillation flask, place it in an 80 °C oil bath for heating, put in a magnetic stirrer, and stir slowly.

[0018] (2) Weigh 1 g of ammonium persulfate in a 10 mL centrifuge tube A, and add 5 mL of ultrapure water.

[0019] (3) Weigh 0.5 g of sodium hypophosphite in a 10 mL centrifuge tube B, add 1 mL of ultrapure water, and then weigh 6.8 g of acrylic acid.

[0020] (4) After shaking the solutions in the two centrifuge tubes A and B, slowly add them to the distillation flask, increase the stirring speed, and carry out condensation reflux. The reaction time is recorded as t1.

[0021] (5) Add 1 mL of ultrapure water to a 1.5 mL centrifuge tube, weigh 0.0135 g of glycidyl methacrylate, shake well and add it to the distillation flask, and continue the reaction for a time recorded as t2.

[0022] (6) Keep warm at 80 °C for 2 h, and the reaction ends.

[0023] 3. Beneficial effects brought by the technical solution of the present invention

[0024] The reaction solution of the aqueous solution polymerization method has a low viscosity, a fast heat transfer rate, and the reaction temperature is easy to control. The polymerization heat can be discharged in time, and there is basically no local overheating phenomenon. Moreover, the initiator and chain transfer agent in the solution are evenly dispersed and are difficult to be wrapped by the polymer. The initiation efficiency of the initiator is high and the molecular weight distribution of the product is relatively narrow. Description of the drawings

[0025] Figure 1 is the 1H NMR spectrum of Sample 1-2, Figure 2 is the 1H NMR spectrum of Sample 1-3, Figure 31H NMR spectrum of sample 2-2 Figure 4 1H NMR spectrum of sample 2-4 Figure 5 1H NMR spectrum of sample 3-4 Figure 6 1H NMR spectrum of sample 4-2 Figure 7 1H NMR spectrum of sample 4-5

[0026] Peaks 1, 2, and 3 are the peaks of glycidyl methacrylate grafted polyacrylic acid. Among them, peak 1 is the characteristic peak of -CH in the side chain; peak 2 is the characteristic peak of -CH2 in the side chain; peak 3 is the characteristic peak of -CH3 in the side chain. It can be seen that the branching of polyacrylic acid is successful. Peak 4 is the characteristic peak of -CH in the main chain of polyacrylic acid; peak 5 is a triplet, which is the characteristic peak of -CH2 in the main chain Specific embodiments

[0027] The properties of different materials were studied by changing the ratio of glycidyl methacrylate to acrylic acid (the first group), the ratio and reaction time t1 (the second group), the reaction times t1 and t2 (the third group), and the mass of ammonium persulfate (the fourth group).

[0028] The first group

[0029]

[0030] The second group

[0031]

[0032] The third group

[0033]

[0034] The fourth group

[0035]

[0036] Characterization and testing

[0037] 1. 1H NMR

[0038] Weigh about 10 mg of polyacrylic acid, dissolve it in about 0.5 mL of heavy water, transfer it to an NMR tube, seal the NMR tube, and then conduct NMR testing

[0039] The grafting rate of glycidyl methacrylate grafted polyacrylic acid was calculated based on peaks 1, 4, and 5. From the 1H NMR spectrum of sample 1-2, it can be seen that the area A1 of peak 1 is 147.69, the area A4 of peak 4 is 2234.24, the area A5 of peak 5 is 4289.24, and the ratio of peak 5 to peak 4 is about 2, which is consistent with the hydrogen ratio of -CH2 to -CH in the main chain. The calculation formula for the grafting rate g is

[0040]

[0041] It can be seen from the 1H NMR spectra of Samples 1-3 that the area A1 of Peak 1 is 16.57, the area A4 of Peak 4 is 887.13, and the area A5 of Peak 5 is 1741.85. The calculation formula for the grafting rate g is:

[0042]

[0043] It can be seen from the 1H NMR spectra of Sample 2-2 that the area A1 of Peak 1 is 29.01, the area A4 of Peak 4 is 1042.87, and the area A5 of Peak 5 is 2031.02. The calculation formula for the grafting rate g is:

[0044]

[0045] It can be seen from the 1H NMR spectra of Sample 2-4 that the area A1 of Peak 1 is 10.97, the area A4 of Peak 4 is 817.78, and the area A5 of Peak 5 is 1650.45. The calculation formula for the grafting rate g is:

[0046]

[0047] It can be seen from the 1H NMR spectra of Sample 3-4 that the area A1 of Peak 1 is 67.15, the area A4 of Peak 4 is 2080.58, and the area A5 of Peak 5 is 3779.47. The calculation formula for the grafting rate g is:

[0048]

[0049] It can be seen from the 1H NMR spectra of Sample 4-2 that the area A1 of Peak 1 is 13.47, the area A4 of Peak 4 is 1066.34, and the area A5 of Peak 5 is 2087.60. The calculation formula for the grafting rate g is:

[0050]

[0051] It can be seen from the 1H NMR spectra of Sample 4-5 that here the grafting rate is calculated using Peak 2 and Peak 4. The area A2 of Peak 2 is 19.19, the area A4 of Peak 4 is 1040.17, and the area A5 of Peak 5 is 2034.11. The calculation formula for the grafting rate g is:

[0052]

[0053] 2. Determination of Scale Inhibition Performance

[0054] Here, the calcium carbonate deposition method is used to determine the scale inhibition performance of the water treatment agent. The specific steps are as follows:

[0055] (1) Preparation of borax buffer solution: Weigh 3.8 g of sodium tetraborate decahydrate, dissolve it in a beaker, transfer it to a 1000 mL volumetric flask, make up to the mark with water, and shake well.

[0056] (2) Preparation of sodium bicarbonate standard solution: Weigh 25.2 g of sodium bicarbonate, dissolve it in a beaker, transfer it to a 1000 mL volumetric flask, make up to the mark with water, and shake well.

[0057] (3) Preparation of calcium chloride standard solution: Weigh 16.7 g of calcium chloride, dissolve it in a beaker, transfer it to a 1000 mL volumetric flask, make up to the mark with water, and shake well.

[0058] (4) Preparation of water treatment agent solution: Weigh 0.625 g of PAA, dissolve it in a beaker, transfer it to a 250 mL volumetric flask, make up to the mark with water, and shake well.

[0059] (5) Add 300 mL of deionized water to a 500 mL conical flask, add 20 mL of borax solution, 20 mL of sodium bicarbonate solution, 20 mL of calcium chloride solution and 3 mL of water treatment agent solution with a pipette, add 140 mL of deionized water, and shake well.

[0060] (6) Place it in a constant temperature water bath at 80 °C for 10 h. After cooling to room temperature, filter it with a medium-speed quantitative filter paper.

[0061] (7) Pipette 25 mL of the filtrate into a 250 mL conical flask, add 50 mL of deionized water, 5 mL of potassium hydroxide (20%) and 0.1 g of calcium-carboxylic acid indicator, and titrate with disodium ethylenediaminetetraacetate solution until the solution changes from purple-red to blue as the end point.

[0062] (8) The scale inhibition performance of the water treatment agent is denoted by η, and the value is expressed in %, and is calculated according to the following formula:

[0063] η = (ρ2 - ρ1) / (ρ - ρ1)

[0064] ρ2: The value of the calcium ion mass concentration after the test of the test solution added with the water treatment agent, in milligrams per milliliter,

[0065] ρ2: The value of the calcium ion mass concentration after the test of the blank test solution without adding the water treatment agent, in milligrams per milliliter, ρ: The value of the calcium ion mass concentration in the actual working condition water or the prepared water, in milligrams per milliliter.

[0066] The content of calcium ion is calculated by mass concentration according to the following formula:

[0067] ρ3 = V1cM / V

[0068] ρ3: The mass concentration of calcium ion,

[0069] V1: The volume of disodium ethylenediaminetetraacetate solution consumed in the titration,

[0070] c: Concentration of disodium ethylenediaminetetraacetate solution,

[0071] M: Molar mass of calcium ions,

[0072] V: Volume of the taken calcium chloride standard solution.

[0073] The first group

[0074]

[0075] We obtained the polyacrylic acid samples of this group by changing the ratio of acrylic acid to glycidyl methacrylate. It can be seen that there is a certain gap between the scale inhibition rate of polyacrylic acid and the standard sample, but they are also very close, showing certain application prospects. Among them, when the ratio of acrylic acid to glycidyl methacrylate is 1000:2, the scale inhibition performance of polyacrylic acid is the best, that is, the scale inhibition performance of sample 1-2 is better than that of other samples. Sample 1-2 was selected for subsequent research.

[0076] The second group

[0077]

[0078] We obtained the polyacrylic acid samples of this group by changing the ratio and reaction time t1. It can be seen that when the ratio is 1000:2 and t1 is 4h, the scale inhibition performance of polyacrylic acid is the best, that is, the scale inhibition performance of sample 2-2 is better than that of other samples, further verifying that the scale inhibition performance of polyacrylic acid is the best when the ratio is 1000:2.

[0079] The third group

[0080]

[0081] We obtained the polyacrylic acid samples of this group by reaction times t1 and t2. It can be seen that changing reaction times t1 and t2 did not significantly improve the scale inhibition rate of polyacrylic acid, and still the scale inhibition performance of sample 1-2 is the best.

[0082] The fourth group

[0083]

[0084] We obtained the polyacrylic acid samples of this group by changing the mass of ammonium persulfate. It can be seen that changing the mass of ammonium persulfate has little effect on the scale inhibition rate, so it is not considered in the subsequent improvement of the performance of polyacrylic acid.

Claims

1. Select ammonium persulfate and sodium hypophosphite as initiators and water as solvent. This reaction generates a lot of heat. When adding acrylic acid, the dropping speed should be controlled to avoid instantaneous generation of a lot of heat.

2. Glycidyl methacrylate used for branching is added into the system after a period of polymerization.

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